Freight transport is the physical process of transporting commodities, merchandise goods and cargo using various vehicles. For example, air freight transports cargo in specialized cargo aircraft and in the luggage compartments of passenger aircraft. Recently, people attempt to use smaller electrical aircraft to rapidly deliver parcels and packages to millions of customer's households. The most promising aircraft is Unmanned Aerial Vehicles (UAVs), which are unpiloted aircraft that are either controlled remotely or flown autonomously along pre-programmed flight plans. UAVs are commonly categorized based on their design and performance specifications spanning a range from miniature low altitude aircraft through large High Altitude Long Endurance (HALE) vehicles. Small low altitude UAVs (AKA drones) is preferred for civil delivery system.
However, there are still some challenges posed in the design, manufacturing, and operation of the UAVs. One of such challenges is the flight endurance of UAVs. In aviation, endurance is the maximum length of time that an aircraft can spend in cruising flight. Endurance is different from range, which is a measure of distance flown. For example, a typical sailplane exhibits high endurance characteristics but poor range characteristics.
Even if powerful batteries such as lithium ion battery are used for the UAVs, they may not provide enough power for the aircraft to haul heavier packages over longer period of time. As a result, the payload capability of delivery UAVs is severely limited to lighter packages within shorter distance. Lacking of payload/weight flexibility becomes a problem needs to be solved by the UAV shipping industry.
Advantageously, the present invention meets the challenge, and provides a solution to overcome the endurance problem.